The apparatus of this invention provides a retrofit substitute for the midsection and the lower unit of a standard outboard motor, having a substitute closed-loop cooling system with an exterior heat exchanger, a substitute oil reservoir, a substitute exhaust system, and a substitute propulsion system, allowing an existing standard outboard-motor powerhead to be used in conditions not conducive to standard open-loop water cooling, such as shallow-water, muddy-water, obstructed-water, seawater, or corrosive-water conditions.
The apparatus of this invention was designed in part because boats that navigate inland waterways, coastal marshes, and swamps encounter areas that are shallow, sometimes filled with invasive vegetation, or silted up with mud that is too soft to walk in or use any other sort of vehicle to access. Boats, particularly shallow draft boats, are the only vehicle practical to access these areas, but outboard motors become useless once they travel outside channels deep enough for cooling and exhaust systems to work properly. Also, the lower unit gearbox section is not designed to deflect obstructions, or is designed intended for rugged use when encountering submerged obstructions such as mud, logs, sand, and so forth.
There are boat motors built for use in these areas and situations, called “shallow water outboards” or, alternatively, “mud motors.” The powerheads used presently are air-cooled engines, commonly used on lawn mowers, portable generators, and pressure washers. A well-known problem in the art is that these engines are very limited in horse power, with the highest-available horsepower engine in this class quite low in comparison to conventional outboard motors on the same size and type of boats. The demand for higher horsepower shallow-water outboard motors has been present for many years with no solution.
Outboard motors have been in production and use for over 100 years, and have become very popular, efficient, and reliable. However, they are limited to clean, deeper channels.
Outboard motors would be an acceptable alternative to the limited horsepower air-engines, but were designed and are built specifically for raw water cooling outboard lower ends. As part of this design, the outboard engine crankshaft has no external shafting. The crankshaft does not extend out of the engine base like the presently used air-cooled engines, and only accepts the driveshaft of its intended mate, the outboard motor lower unit. It is water cooled, with its water pump being built into its mate, the lower unit. The outboard-motor powerhead has no exhaust system except for its mate, the conventional lower unit and midsection. The exhaust travels through the midsection and out of the lower unit. This hot exhaust is cooled by raw cooling water after it has been supplied to the powerhead, and exiting the cooling jackets of the powerhead. Thus, while the outboard-motor powerhead is compact, lightweight, and reliable, it is not considered to be an option for shallow water outboard motors, or any other machinery, because it was designed and built with the outboard motor midsection and lower unit as a necessary part of the complete operable engine.